RETRACTION

Volume 62, no. 8, e02356-17, 2018, https://doi.org/10.1128/AAC.02356-17. We hereby retract this article. In our paper we described that growth of an EF4 knockout strain of Escherichia coli is less susceptible to tetracycline than its wild-type parent. However, when repeat experiments were performed comparing additional EF4 knockout strains and their parent strains (previously described and provided by R. Balakrishnan, K. Oman, S. Shoji, R. Bundschuh, and K. Fredrick, Nucleic Acids Res 42:13370-13383, 2014, https://doi.org/10.1093/nar/gku1098), we could not observe similar behaviors. Upon repeating experiments using the EF4 knockout E. coli strain (JW2553) and its parental strain (BW25113) obtained from the Keio collection (T. Baba, T. Ara, M. Hasegawa, Y. Takai, Y. Okumura, M. Baba, K. A. Datsenko, M. Tomita, B. L. Wanner, and H. Mori, Mol Syst Biol 2:2006.0008, 2006, https://doi.org/10.1038/msb4100050), we found that only the JW2553 strain is more resistant to tetracycline. Introducing plasmids expressing EF4 into the JW2553 strain abolishes tetracycline resistance. Although all experimental results reported in our article were reproducible, the finding that the tetracycline resistance is strain specific means that key conclusions in our article are in question. At this stage, we are unable to identify which additional, unknown factors of the JW2553 strain contribute to its EF4-dependent tetracycline resistance, and as a result we retract the paper.